I am going to be making 10 gallons of Helles German Lager. Last week I made 6 gallons of the exact recipe, using the same OG, mashing schedule hop schedule. Half of this I canned for future starters in mason jars. The other half I pitched a XL smack pack of Wyeast (Bavarian lager). Its been fermenting for a little under a week at 50F. My plan is to split the 3 gallons for 2 brew sessions. I was planning to stir it up, and pitch half the beer this week, and half the beer next week for my 10 gallon batches.

My question is: Can I pitch half of it this week, even though its still fermenting away, or should I wait until it has fermented out, crash cool and pitch only half of the slurry?

Ideally, you should have made a half gal starter and decanted the wort after it fermented and then pitched it into the 3 gallons. Then you could have racked the 3 gal to secondary and had an extra 3 gal of beer.

At this point, you could let the beer ferment out and decant before repitching, or OTOH, pitch the fermenting beer into your new batch. Being that its active, that may be the best thing to do. Be sure and aerate well.

I'm hoping that's OK. It was my original plan. Do you think that 1.5 gallons of "beer" will affect a 10 gallon batch greatly? Theoretically, it should be the same beer I'm adding since the recipe, mashing, hoping and fermentation are the same.